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UltravioletPhotography

Leptosyne californica [California Tickseed]


Andrea B.

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Blum, A.G. (2014) Leptosyne californica Nutt. (Asteraceae) California Tickseed. Flowers photographed in ultraviolet and visible light. http://www.ultravioletphotography.com/content/index.php/topic/1119-leptosyne-californica-california-tickseed/

 

Joshua Tree National Park, California, USA

04 March 2012

Wildflower

 

Synonyms:

  • Coreopsis californica (Nutt.) H. Sharsm.

Comment:

This wildflower of the southwestern desert is usually found in washes and open areas. Unlike the UV-dark common garden Tickseed, this flower has UV-bright notched tips.

 

Reference:

1. Jepson eFlora (6 Dec 2014) L. californica Nutt. Jepson Herbarium, U. of Cal.-Berkeley, Berkeley, CA. http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=30645

 

Visible Light [f/xxx for 1/xxx" @ ISO XXX with Nikon D3S + Nikon 60mm f/2.8G Micro-Nikkor]

The threadlike leaves of L. californica are basal.

leptosyneCalifornica030412joshuaTreeNpCA_35014pfV2.jpg

 

Visible Light [f/xxx for 1/xxx" @ ISO XXX in Sunlight with Baader UVIR-Block Filter]

leptosyneCalifornicaVisSun030412joshuaTreeCA_22843origProofPn01.jpg

 

Ultraviolet Light [f/xxx for 1/xxx" @ ISO XXX in Sunlight with Baader UV-Pass Filter]

leptosyneCalifornicaUVBaadSB14030412joshuaTreeCA_22856origProofPn01.jpg

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Man that is dark.

With that light background in UV, it might stand out as much as something with a UV signature that included the typical bulls-eye.

 

-D

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It would also be a distinctive color in a GBU shot that might be uncommon in its environment..I suspect bright red or orange. Dogwood sepals are somewhat similar in UV but white in visible (=yellow in GBU.)
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Damon, we have indeed speculated about exactly that: UV-dark flowers against the desert's UV-light background. And I have also seen it mentioned somewhere in the literature.

 

Clark, is GBU = green/blue/ultraviolet? I am not sure from where comes the bright red or orange you mention?

 

A bee would see the dark area of this UV-absorbing visible yellow tickseed flower as the bee colour "green" because only its green visual receptor would be stimulated in the dark area.

The brighter tips of the flower would be seen by the bee as the bee colour "UV-green", which we have no way to represent.

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Yes, here is a GBU-->RGB of the Biltmore House:

 

post-66-0-55547400-1416880843.jpg

 

This kind of image is the analogue of the more familiar IRG "color infrared" image, but unlike the latter has no historical film basis nor any particular practical application I know of; it is mainly a curiosity. The green band on the water here is a chronochromic artifact. In this kind of image, pure yellow becomes red because only the green light is recorded which displays as red (the actual red is not displayed.) If some blue light mixes in you get orange.

 

I assumed that the apparent bright tips on the tickseed flower were specular reflections; forgive me if this is incorrect.

 

I am not an expert in insect vision but know that their wavelength channels do not map onto ours in any simple way; I am a bit lost in discussions of this.

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So here's one of those "answers to everything" questions, to which the answer in Hitchhikers Guide was 42.

 

Looking at a flower which appears visible yellow, how can we guess whether it will be UV-yellow (almost the default case) or if it will be UV-black as occurs in most Australian cases?

 

Dave

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To the best of my knowledge and field experience, one cannot predict the answer in this case, Dave. Visible yellow flowers can in UV photography [using standard processing] appear black, partially black, greyish, greenish tinged, very pale yellow, pure yellow, or even with a slight orange hue to them. If they do appear UV black all over, it is quite common to see the "shimmering" effect of conical cells on whole or parts of the corolla.
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Clark: The tips of this flower which appear (false) yellow are UV-reflective. If the L. californica is photographed from other angles, those reflective tips will still be seen. So it is not specular.

There are some simple models of bee vision which give good insights. I stockpiled some references and notes about bee vision here:

http://www.ultravioletphotography.com/content/index.php/topic/324-bee-vision-notes-and-colour-charts/

 

Dave: No way to tell ahead of time how a flower will exhibit its UV-signature. Sometimes, flowers within a genus show similar UV-signatures. But not always. See for example the other Leptosyne from the desert: Leptosyne bigelovii

Bjørn and I had fun trying to "predict" the UV-signatures on the Desert Wildflower Safari 2012.

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Bill De Jager
Andrea, that is one cool-looking flower! I don't mean the black appearance all over, I mean what looks (at this resolution) like sparkles on the parts of the disk flowers. Did you see shimmering in these areas when viewing the flower?
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So cool this stuff.

Re:A bee would see the dark area of this UV-absorbing visible yellow tickseed flower as the bee colour "green"

So if most of the area visible to the bee is "green", how is that an advantageous thing for the flower?

 

-D

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So if most of the area visible to the bee is "green", how is that an advantageous thing for the flower?

 

I don't know who or what pollinates this Leptosyne species. So I do not know whether its UV-signature is advantageous to it or not. I like to think that its UV-signature is meaningful somehow because nature doesn't evolve disadvantageously. But it could be that the underlying pigments causing the UV-signature are the advantage in some bio-chemical way.

 

I know I did mention bees above, but perhaps I should have said that any animal/insect having UV, blue and green visual receptors would see this Leptosyne as green because only its G visual receptor would be stimulated. We can't say whether it would appear as a dark green or a light green or a saturated green, etc., to the animal/insect without knowing the spectral measurement of the flower rays and disk and subsequently interpreting that against the biology of animal/insect's vision. (For example, some animals/insects interpret brightness and contrast differently from our human vision and to them the designations 'light' and 'dark' are meaningless.) Regardless of these various factors, the Leptosyne will stand out against the desert background when seen by UV-sighted creatures and by our converted cameras through a UV-pass filter.

 

Did you see shimmering in these areas when viewing the flower?

Not in the visible spectrum.

In the UV photograph what you are seeing on the flower is this:

(1) In the center of the disk, the small still-closed disk flowers have UV-bright tips which appear like bright dots. After the disk flowers open up, the tips form bright curved patterns on the edges of the disk.

(2) The pollen on the clustered anthers of the opened disk flowers is also UV-bright.

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